[FFmpeg-trac] #4764(build system:new): Problems when compiling with msvc toolchain and with other libraries.

[FFmpeg]

#4764: Problems when compiling with msvc toolchain and with other libraries.
-------------------------------------+-------------------------------------
             Reporter:               |                     Type:  defect
  ashegoulding                       |                 Priority:  wish
               Status:  new          |                  Version:  git-
            Component:  build        |  master
  system                             |               Blocked By:
             Keywords:  MSVC         |  Reproduced by developer:  0
  toolchain                          |
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 1. The library tests can't work with cl.exe.
 2. Runtime library specification is necessary even for static builds.
 (See last section for details)


 How to reproduce:
 {{{
 % vcvarsall.bat
 % export LIB="X:\pathto\externlibs\lib;$LIB"
 % export INCLUDE="X:\pathto\externlibs\include;$INCLUDE"
 # MT, with no msvcrt DLL
 % ffmpeg -i input ... output
 ./configure --toolchain=msvc --enable-gpl --enable-nonfree --enable-nvenc
 --enable-libvorbis --enable-libmp3lame --enable-libtheora --enable-libx264
 --enable-libx265 --enable-libxvid --enable-static --disable-shared
 --disable-debug --extra-cflags="-MD" --extra-cxxflags="-MD" --extra-
 ldflags="/nodefaultlib:libcmt.lib" --extra-libs="libmp3lame-static.lib
 libtheora_static.lib libxvidcore.lib zlib.lib libmpghip-static.lib
 libvorbis_static.lib x265-static.lib libogg_static.lib libx264.lib"
 # MD, with msvcrt
 ./configure --toolchain=msvc --enable-gpl --enable-nonfree --enable-nvenc
 --enable-libvorbis --enable-libmp3lame --enable-libtheora --enable-libx264
 --enable-libx265 --enable-libxvid --enable-static --disable-shared
 --disable-debug --extra-cflags="-MT" --extra-cxxflags="-MT" --extra-
 ldflags="/nodefaultlib:msvcrt.lib" --extra-libs="libmp3lame-static.lib
 libtheora_static.lib libxvidcore.lib zlib.lib libmpghip-static.lib
 libvorbis_static.lib x265-static.lib libogg_static.lib libx264.lib"
 }}}


 MSVC compiles just fine when it compiles just ffmpeg it self. But when it
 comes to compile with other libraries enabled, it goes into chaos.

 1. The library tests when using MSVC toolchain
 The script builds test programs for enabled libraries to check if they are
 available with the given toolchain. For example, to see libmp3lame, it
 compiles following code:
 {{{
 #include <lame/lame.h>

 int main(){
 lame_set_VBR_quality();
 return 0;
 }

 }}}

 specified by configure script line:
 {{{
 enabled libmp3lame        && require "libmp3lame >= 3.98.3" lame/lame.h
 lame_set_VBR_quality -lmp3lame
 }}}

 The problem is, link.exe somehow doesn't know what to link and complains
 with error. Yes, the full prototype for the function is:

 int lame_set_VBR_quality(lame_global_flags *, float)

 Removing these checks(see attachment) solves this problem and the
 compilation never fails under the circumstance that libraries are properly
 set in LIB and INCLUDE vars.


 2. Runtime library links
 MSVC toolchain links what runtime library to use when COMPILE TIME, NOT
 link time. So /MD and /MT switches are in compiler settings not in linker
 settings.
 If you have to link MT on your program that links ffmpeg-libs, linking
 ffmpeg-libs compiled with /MD won't work because of the external
 libraries. Linking will fail. You need to link MT version of ffmpeg-lib
 for MT programs or DLLs and vice versa.
 As you can see on the "How to reproduce" section, you can compile and link
 MT as mentioned and the other libraries that ffmpeg uses.


 If someone could fix these problems, we could use use MSVC to compile
 ffmepg freely, without using painful mingw toolchains.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/4764>
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